A small percentage of pregnant women will develop elevated body temperature during labor. This is slightly more common in women who are having their first baby and long labors, and use epidural anesthesia. Much research has shown that it is very unlikely that it truly reflects infection in either mother or baby. However, in some cases, the pediatricians may do some blood tests on the baby to rule out any possibility of infection. Rest assured that most women do not develop fever during labor either with or without epidural anesthesia, although you should be aware that this finding is more common in patients who use epidural anesthesia for labor and delivery. The most recent data shows that elevated temperatures occur in 24% of women having their first baby and using epidural anesthesia compared to 5% in women without epidural anesthesia. No difference was found in women having second or subsequent deliveries.

The mechanism for this observation is not known. It may be related to the way body heat is generated and distributed during labor and delivery. During painful labor the patients tend to breath very fast and this may allow heat to be dissipated away from the body. Once the pain relief has been obtained, breathing tends to be more calm and relaxed; eventually the body temperature may rise.

References:

ACOG (American College Of Obstetricians and Gynecologists) Practice Bulletin on Obstetric Analgesia and Anesthesia. July 2002;36:177-191.